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Old 11-03-2013, 04:11 PM   #1
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Default 2 Ignition Coil Failures

I tried posting this on miata.net first to try and get an answer instead of annoying you guys, but I need smarter answers so I came here

So I first purchased my car a little over a year ago, and it started hesitating on start up, eventually getting worse progressing to low mpg's due to running rich. Finally, one day it simply quit, and was misfiring VERY bad. Ordered an OEM coil pack (my oh my they are expensive....) and the problem was gone, starting was great, and mpg's back up! Now, it's been around 6 months since I replaced it, and recently I have been getting the same symptoms. You could run a second miata off of my exhaust fumes it is so rich....but only sometimes. It seemed to be intermittent. Also, sometimes I get a good strong start, other times it takes a couple extra seconds. I had the ignition coil replaced, and what do you know, working like a charm again.

So here is the question for those of you who know more than me, is this "coincidence" or could there be an issue with the stock ECU that is changing my dwell time, overheating the pack and killing the unit? I don't want to replace ANOTHER coil if there is something wrong again. I am building a MS DIYPNP in the coming month, so I really want my car working properly before I get confused as to what I am doing wrong for the build. Ideas?

*edit* it is a 2000 NB, non FI....at least till I get the DIYPNP working.
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Old 11-03-2013, 06:22 PM   #2
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Hmmm . . . aren't the 99-00s known to eat coils? With the cat going soon thereafter?

Since you're building an MS anyway, I would just finish that and move on to COPs and not spend any more money on the weak 99-00 coilpacks.

You might be able to gap your plugs a little tighter to get you by. Something like .025-.030. That will allow a weaker coil to fire them. We do this all the time on the turbo motors to avoid spark blowout (going to COPs or LS coils lets us open the gap back up).
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Old 11-03-2013, 08:31 PM   #3
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I have a 99 I was lucky and didn't have any coil related problems in 20k miles. I did have a main relay go out thought. I went MS3 + cops and ditched the stock ignition. it was a no brainier I bought my cops off ebay with pigtails for $65 shipped.

Note - I think engine bay heat kills the coils (when its it behind the motor - Maybe vibration too since BPs are really noisy) I moved my stock coils to hang off the intake manifold with a custom bracket when I bought the car. Never had one issue or problem with them. anyone that wants to do this also would need honda accord plug wires is what I used. I didn't do this cause of this issue it was because I did a custom coolant reroute and their was no space left behind the motor.
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Old 11-04-2013, 12:52 AM   #4
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99/00 are notorious for eating coil packs. After the pack dies, it dumps unburned fuel into the exhaust and your cat goes Chernobyl. I'm guessing if you can SMELL unburned fuel in your exhaust, your cat is already done, or there is nothing left inside it.

I'm going to start by assuming you have replaced your plug wires sometime during your coil swap shenanigans.



I had the wiring all pulled apart on my 2000 this weekend so its fresh in my mind... the coils, temp sensor and injectors are all connected to the same harness. This harness runs from the rear up to the front of the engine where it attaches to the chassis harness in a 4 pin and a 8 pin connector that are anchored to a metal plate in front of the timing cover. Follow me thus far? Underneath the throttle body there is a steel bracket that attaches to the lower manifold. There are 4 bolts in that bracket: 2 go vertical up under the throttle body somewhere and 2 go horizontally into the lower manifold. On ONE of these two horizontal bolts there is (or should be) a ring terminal with 2 wires attached to it. These are grounds and they are VERY important. These pass DIRECTLY back to the coils. I know this because I had to check continuity on this today.

Corrosion is the bane of automotive electrical. It causes resistance and extra load on components and hastens their demise. This goes double for grounds. The bracket is steel and the bolts are steel, and the ring terminal is some sort of brass while the manifold is aluminum. This means dissimilar metals and a higher probability of corrosion. If you have any corrosion around that ring terminal, do yourself a favor and remove the bolt, polish the ring terminal, polish the surfaces it contacts, coat it all with dielectric grease and reassemble. If the ring terminal looks questionable, replace it with a fresh brass one, don't bother with shitty aluminum ones. I use my dremel with a stainless wheel to do this type of polishing.

Edit: Here, I made you a pretty picture.


Left side of image is rear of engine, right is front. This harness is wedged down between the intake manifold and the head.

Start by checking the ring terminal for corrosion, then open up the 4 pin and 8 pin connectors and check them as well. Check the CRIMP on that ring and make sure its not frayed where the wires pass into the crimp. The 4 and 8 pin connectors "should" look good because they "should" be sealed connectors, but a little bit of dielectric grease never hurt anything.

I can walk you through every connector between the ECU and the coil, but lets start with the easy stuff.
Attached Thumbnails
2 Ignition Coil Failures-qajdhfv.jpg   2 Ignition Coil Failures-gxdgxoz.jpg  

Last edited by EO2K; 11-12-2013 at 06:05 PM. Reason: Pretty pretty picture
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Old 11-04-2013, 01:21 AM   #5
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Also, I see this is your second thread here on MiataTurbo and you are up to 4 posts. Go here and make an intro thread: Meet and Greet - Miata Turbo Forum - Turbo Kitten is watching you test compression. and de-noob thyself. Tell us about your car, yourself, your cat, your mechanical abilities, your performance goals for the car, etc. And for the love of god, and all that is holy, post some pics of your car. We are very visual people.
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Old 11-04-2013, 11:30 AM   #6
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First things first: https://www.miataturbo.net/meet-gree...mpa-bay-75877/

After class I will go and look for those grounds and polish them up. On another recent electrical issue I have went around and polished every ground connector I could find, but it's very possible I missed this one; I don't really remember it. Thanks everyone for the help, and especially you EO2K!
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Old 11-04-2013, 11:52 AM   #7
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First things first: https://www.miataturbo.net/meet-gree...mpa-bay-75877/

After class I will go and look for those grounds and polish them up. On another recent electrical issue I have went around and polished every ground connector I could find, but it's very possible I missed this one; I don't really remember it. Thanks everyone for the help, and especially you EO2K!

Quote:
Originally Posted by EO2K View Post
I'm going to start by assuming you have replaced your plug wires sometime during your coil swap shenanigans.
Even though the wires are a year old (~7k miles) would you still replace them? If I need to it's no problem, I just want to save the $40 if it doesn't really matter.
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Old 11-04-2013, 01:19 PM   #8
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Quote:
Originally Posted by aeathb View Post
Even though the wires are a year old (~7k miles) would you still replace them? If I need to it's no problem, I just want to save the $40 if it doesn't really matter.
Probably not needed. Hit them with an ohmeter and make sure none have high resistance. While there, check your plugs and plug gaps. With rich running, you may have fouled plugs.
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Old 11-04-2013, 01:38 PM   #9
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Quote:
Originally Posted by hornetball View Post
Probably not needed. Hit them with an ohmeter and make sure none have high resistance. While there, check your plugs and plug gaps. With rich running, you may have fouled plugs.
I put on the older coil pack (the weaker one, not the broken one) just to play around and see what changes what. I pulled my plugs and they don't look that bad, a little white and green in some spots but looks pretty normal to me. They were however .053, so I gapped them down to .040. I bought new plugs that I'll put in tomorrow while I am changing my vcg. And I went in there and cleaned the ground leads. Still a little start hesitation, but I'm curious what MPG's will do. I think I'm gana keep the new ignition coil off till I'm done troubleshooting.
Edit: I'll check the wires too while I'm in there!
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Old 11-12-2013, 06:11 PM   #10
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I'm ritarded, there are 8 pins in that connector, NOT 6. I updated the graphic and edited my previous post.

How's things running?
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Old 11-12-2013, 07:05 PM   #11
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With the old coil pack I was getting very poor starts even after changing plugs, cleaning the grounds, and checking wireset for abnormal resistance. I put on the new ignition coil again and so far quicker start ups (But still some hesitation, just not as bad) I haven't smelled anything rich for a while, and MPG's seem to have improved, but I am not through my tank yet (thus I was waiting to post my results). I will hopefully be reporting back soon with good MPG news, but I am concerned why i get abnormal start up times. I live in Gainesville so "cold start" isn't something fair to blame it on, my fuel filter is less than 10k miles old, my plugs, wireset, coils are all new and or good, and my starter cranks hard and is 1k old.....Injectors maybe?
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Old 11-13-2013, 04:13 AM   #12
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I converted to Toyota COPs before changing from the stock ECU, they worked fine for a few months but then developed a misfire. I'm sure it's because of the excessive dwell.

Just thought you'd like to know in case you are tempted to switch them before your new ECU.
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Old 11-13-2013, 04:13 AM   #13
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I converted to Toyota COPs before changing from the stock ECU, they worked fine for a few months but then developed a misfire. I'm sure it's because of the excessive dwell.

Just thought you'd like to know in case you are tempted to switch them before your new ECU.
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Old 11-13-2013, 12:02 PM   #14
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Quote:
Originally Posted by timk View Post
I converted to Toyota COPs before changing from the stock ECU, they worked fine for a few months but then developed a misfire. I'm sure it's because of the excessive dwell.

Just thought you'd like to know in case you are tempted to switch them before your new ECU.
I was reading up on the COP's and saw everyone was using ~2.5ms, but I could not find specs on the stock ECU so I just assumed being wasted spark is was most likely higher. Thanks for the heads up though
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Old 11-13-2013, 02:56 PM   #15
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Yeah, I think the stock ecu puts out something like 5~7ms. I don't remember exactly but I know its something like more than double what the COPs want to see.

There are like 6 wires coming out of the coils

2x black - grounds
2x black/white - power
1x brown/yellow - trigger - Coil 1
1x brown - trigger - Coil 2

Grounds - super simple, I won't go into those again. Kinda obvious where they run.

Power - These are fed via the ENGINE fuse located "FUSE BLOCK - LEFT SIDE UNDER DASH" and the MAIN relay "MAIN FUSE BLOCK - RIGHT REAR OF ENGINE COMPARTMENT." This is also power for things like the heater elements in both front and rear O2 sensors.

Triggers - These wires carry the signal directly from the ECU to the coil.

I made another pretty picture

Note: Connectors 1-8 are things like TPS/IAC/Crank/Cam/AC/Etc that I don't feel like labeling right now

As you can see, the triggers feed through those front connectors and then run DIRECTLY to the ECU. I believe the power passes through the X-22 connector on its way to the ENGINE fuse and MAIN relay. The X-22 is (IIRC) buried somewhere way up under the dash. Of the 3 separate connectors that feed into the ECU, 2 are exclusive to this harness. Check to make sure they are secure and that the previous owner of your car didn't try to install a powercard or something equally stupid with Scotch Taps on any of the wires. I can't remember exactly where the ECU ground connects, but its up there by the throttle body. Be aware of it and if you can find it, it can't hurt to clean it up as well.

Go here: http://www.mellens.net/mazda/index.html
Download the PDFs for:
  • 1999-2000 Engine
  • 1999 Cruise Control
  • 1999 Wiring
  • 2000 Wiring

Also go here: Miata Information
Download the PDFs for:
  • 1999 How to Use Wiring Diagrams
  • 1999 System Wiring Diagrams
  • 2000 How to Use Wiring Diagrams
  • 2000 System Wiring Diagrams
  • Mazda MX-5 Miata 2000 Wiring Diagrams

Save all these bastards locally for future reference. There are some repeats, but they will be obvious once you start looking through them.

There is some more stuff here as well: Miata Forumz - Mazda Miata Chat Forums

Anyway, let me know if there is anything else I can do to help.
Attached Thumbnails
2 Ignition Coil Failures-ugkgo6c.jpg   2 Ignition Coil Failures-mz9u3xc.jpg  

Last edited by EO2K; 11-13-2013 at 03:38 PM.
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Old 11-14-2013, 01:01 AM   #16
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Quote:
Originally Posted by EO2K View Post
Yeah, I think the stock ecu puts out something like 5~7ms. I don't remember exactly but I know its something like more than double what the COPs want to see.

There are like 6 wires coming out of the coils

2x black - grounds
2x black/white - power
1x brown/yellow - trigger - Coil 1
1x brown - trigger - Coil 2

Grounds - super simple, I won't go into those again. Kinda obvious where they run.

Power - These are fed via the ENGINE fuse located "FUSE BLOCK - LEFT SIDE UNDER DASH" and the MAIN relay "MAIN FUSE BLOCK - RIGHT REAR OF ENGINE COMPARTMENT." This is also power for things like the heater elements in both front and rear O2 sensors.

Triggers - These wires carry the signal directly from the ECU to the coil.

I made another pretty picture

Note: Connectors 1-8 are things like TPS/IAC/Crank/Cam/AC/Etc that I don't feel like labeling right now

As you can see, the triggers feed through those front connectors and then run DIRECTLY to the ECU. I believe the power passes through the X-22 connector on its way to the ENGINE fuse and MAIN relay. The X-22 is (IIRC) buried somewhere way up under the dash. Of the 3 separate connectors that feed into the ECU, 2 are exclusive to this harness. Check to make sure they are secure and that the previous owner of your car didn't try to install a powercard or something equally stupid with Scotch Taps on any of the wires. I can't remember exactly where the ECU ground connects, but its up there by the throttle body. Be aware of it and if you can find it, it can't hurt to clean it up as well.

Go here: http://www.mellens.net/mazda/index.html
Download the PDFs for:
  • 1999-2000 Engine
  • 1999 Cruise Control
  • 1999 Wiring
  • 2000 Wiring

Also go here: Miata Information
Download the PDFs for:
  • 1999 How to Use Wiring Diagrams
  • 1999 System Wiring Diagrams
  • 2000 How to Use Wiring Diagrams
  • 2000 System Wiring Diagrams
  • Mazda MX-5 Miata 2000 Wiring Diagrams

Save all these bastards locally for future reference. There are some repeats, but they will be obvious once you start looking through them.

There is some more stuff here as well: Miata Forumz - Mazda Miata Chat Forums

Anyway, let me know if there is anything else I can do to help.
Wow, you covered pretty much everything! I sincerely appreciate the help!
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Old 11-14-2013, 12:23 PM   #17
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Quote:
Originally Posted by aeathb View Post
Wow, you covered pretty much everything! I sincerely appreciate the help!
You challenged us to be better than m.net
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Old 11-18-2013, 10:36 PM   #18
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So Update: MPG's are just as bad as before I changed the ignition coil for the second time, put in correctly gapped plugs (.040"), checked wireset with ohmmeter, and cleaned the ECU/ignition coil/etc grounds. Now, as an "Added Bonus!!" my car is having a really hard time starting. It sounds very weak kicking in. Just as before there are no CEL codes (pending or stored). FWIW I do not smell raw gas as before, but I am kinda running out of ideas. Could it be the injectors? I am installing my WBO2 a little bit early this week so that I can see what my AFR's are doing at idle and at driving around. Any tests anyone can think of doing? This is quite frustrating.... Edit: I should note the car only has starting troubles about 50% of the time.

Last edited by aeathb; 11-19-2013 at 12:05 AM.
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Old 11-18-2013, 11:19 PM   #19
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Is your cat still in one piece? Do you have the CA Emissions pre-cat?
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Old 11-18-2013, 11:21 PM   #20
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Cat in 1 piece and was replaced under 6 months ago (yea, quite a bit has been replaced lol), and resonator removed. No CA Pre-cat. Originally by researching I had that on my list of possibilities, but I did not get a CEL for the O2 sensor, and more importantly I have not lost top end power.

Last edited by aeathb; 11-19-2013 at 12:04 AM.
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